The Role of Defects and Interface Degradation on Ferroelectric HZO Capacitors Aging

Abstract

The discovery of ferroelectricity in HfO2based materials, especially Hf0.5Zr0.5O2 (HZO), opened to a wide range of applications. In fact, innovative HZO memories, such as ferroelectric tunnel junctions (FTJs), are suitable candidates as ultra-low power storage/synaptic elements, holding the data as a polarization state. Yet, a clear link between the device degradation and material/interface properties is still lacking. In this work, we elucidate the degradation dynamics in metal-HZO-metal (MFM) capacitors by combining ab-initio calculations, physics-based simulations, dedicated experiments, and custom data analysis based on a recently introduced small-signal device model. Stress/measure experiments are conducted to: i) extract the 2𝑷 𝒓 (remnant polarization) evolution throughout device lifetime (from pristine to wake-up and fatigue); ii) determine parasitic series impedance and key material properties through a small-signal model; iii) evaluate the leakage current. Including the contribution of the parasitic series impedance in physics-based simulations allows reproducing leakage profiles and their cycling evolution. The combination of the proposed approaches allows to better interpret the behavior of these devices and retrieve the key role of process conditions (specifically post-deposition steps) in determining the device lifetime and overall reliability.